1. Field of the Invention
This invention relates to a process for the preparation of certain indanols and is more particularly concerned with a process for the cycli-dimerization reaction of certain isopropenylphenols and derivative forms thereof to said indanols and with processes for the conversion of phenol to certain indanols which incorporate this cyclization as a step therein.
2. Description of the Prior Art
Certain dihydric indane compounds, particularly hydroxyphenyl-indanol compounds, have been known for some time along with their use in the formation of epoxide resins and as antioxidants in rubber products. U.S. Pat. Nos. 2,754,285 and 2,819,249 disclose the preparation of these compounds via the acid catalyzed dimerization of .alpha.-methylstyrenes to form indanes, followed by sulfonation of the indanes, and subsequent fusion of the sulfonated products with potassium hydroxide. The troublesome steps of ring sulfonation followed by alkali fusion were eliminated when Petropoulos et al (U.S. Pat. No. 2,979,534) discovered that the isopropenylphenol products obtained from the cracking of certain bisphenols could be dimerized at temperatures ranging from 110.degree. C.-160.degree. C. to provide hydroxyphenyl-indanols directly, or, alternatively, that the cracking and dimerizing reactions could be carried on simultaneously within the temperature range of 130.degree. to 160.degree. C. Howard (U.S. Pat. No. 3,271,463) observed the formation of a small amount of 1-(p-hydroxyphenyl)-1,3,3-trimethyl-6-indanol along with the main product of 3,3,3',3'-tetramethyl-1,1'-spiro-6-indanol when bisphenol A was contacted with aqueous sulfuric acid at 90.degree.-150.degree. C.
U.S. Pat. No. 3,264,357 discloses the preparation of bis-phenols via the reaction of the mixture of the two isomeric forms of the dimer of isopropenylphenol with a phenol in the presence of a strong acid catalyst including trichloroacetic acid. This disclosure reports the formation of a hydroxyphenyl-indanol when the subject reaction is carried out in the absence of the phenol consistuent at a reaction temperature of about 90.degree. C. U.S. Pat. No. 3,264,358 reports the preparation of 1-(p-hydroxyphenyl)-1,3,3-trimethyl-6-indanol when a mixture of the two isomeric dimers of p-isopropenylphenol are treated with a strong acid catalyst. Specifically, the dimer mixture was heated under reflux with concentrated hydrochloric acid for 2 hours.
U.S. Pat. No. 3,288,864 discloses the reaction of isopropenylphenol in the presence of Friedel-Crafts catalysts to form hydroxyphenyl-indanols at elevated temperatures.
Japanese specification No. 78 68762 (Chem. Abst. 89, 1978, 146656c) discloses the cyclization of p-isopropenylphenol in aromatic hydrocarbons or halohydrocarbons containing nitro or cyano compounds above 50.degree. C. and in the presence of alkylating catalysts, i.e. iodine, perchloric acid, aluminum chloride, etc.
I have now discovered that, by using a certain class of strong organic acids, which serve as both solvent and catalyst, isopropenylphenols and derivative forms thereof can be converted very easily into the corresponding hydroxyphenyl-indanol compounds. Surprisingly, the conversion is very rapid, much more rapid than prior art methods, and can be accomplished at temperatures as low as normal room temperature (about 20.degree. C.) to provide the indanols in high yields and in excellent purity.
More surprisingly, the isopropenylphenol starting material need not be in the monomeric state but can be in the derivative form of the dimer, the trimer, and higher oligomer forms, yet still be converted to the dihydric indane products in accordance with the present methods and in the same high yields as when the monomeric phenol is employed.
To the best of my knowledge, there is no known prior art method which can convert the subject isopropenylphenols and their oligomeric derivative forms into the corresponding indanols in such high yields and good purity, using such mild reaction conditions and at such a rapid rate. Generally speaking, typical prior art methods (see Example 8 below which is in accordance with Example 2 of U.S. Pat. No. 3,264,358) result in much lower yields than the instant methods.
In another unexpected aspect of the present invention, I have found that the method in accordance with the present invention is particularly useful in a semi-continuous process in which phenol is condensed with a ketone to yield a bisphenol compound, the bisphenol is subjected to alkaline pyrolysis to yield a mixture of phenol and a p-isopropenylphenol compound. Distillation of the mixture to recover the regenerated phenol leaves a residue comprised of a mixture of the p-isopropenylphenol and its dimerized form as the major components. The latter mixture is subjected to the method of this invention to obtain the corresponding hydroxyphenylindanol and the regenerated phenol compound is reused in a further cycle of operations.